Thanks for an insightful post!
I’ve thought some more about this, and googled around a little, and I’m starting to think of these two variants as different views onto the same thing, with different benefits.
To me the tonal center movable do captures the melody better, because it’s super clear from the syllables how that is developing. The downside is that it’s like you’re singing that melody to a drone. The information about the chord changes that are flying by aren’t encoded anywhere.
If on the other hand you move the do with the chord changes, then it’s less clear how the melody moves, because that’s no longer encoded explicitly. E.g. Autumn Leaves:
Do Re Me | Me | Do Re Mi | Mi | Do Re Me | Me | Do Re Mi | Me
Without knowing the chords you can’t sing this at all! The upside is that it’s quite clear how each melody note is going to sound in relation to the underlying chord.
According to another interwebber, over here, an interesting thing starts to happen if you already know the melody (and your solfege) and sing it in this manner: you’ll start to hear the implicit dos in your head at the same time and can experience both the melody and the harmony simultaneously!
I think I’m going to be using the tonal center movable do quite a bit, because it’s such a powerful tool for transcription. But I still think it makes more sense to encode vocabulary using a do that moves with the chord, because that should make it a lot easier to pre-hear what the lick is going to sound like over some chord.
Am I wrong on this? Do you find it effortless to pre-hear G, B, D, F over a G7 as so, ti, re, fa?